1. Field of the Invention
The present invention relates to a wafer polishing apparatus which polishes a wafer by a Chemical Mechanical Planarizer (CMP).
2. Description of the Related Art
A film which is composed of copper (called a Cu film) and is polished by the CMP tends to be deposited at the center or at the outer periphery of a wafer W as seen in FIGS. 8(A), 8(B) and 8(C), since a current deposition technology yet remains to be improved. For that circumstances, there is a method for flattening the wafer having irregular film thicknesses by varying the pressing forces of a carrier at different areas. More specifically, machining amounts are made different depending on parts of the wafer by giving a variation in the pressing forces of the carrier at different areas thereof in order to make the thickness of the entire film uniform and at the same time remove a film of unnecessary parts of the wafer.
Japanese Patent Application Publication No. 9-225821 discloses a method in which plural openings for spouting compressed air to the bottom face of the carrier (i.e., a holding face of the wafer), and the plural openings are assigned to plural areas so as to supply the compressed air to the respective areas, whereby the pressing force is varied at different areas.
In another method, plural air bags that are assigned to plural areas are provided to the bottom of the carrier, and air bags for pressing the wafer have varied pressing forces for the respective areas to be pressed.
In the conventional methods, however, an entire carrier must be replaced by another after a pressure variation has been set once, in a case where the setting must be changed. Moreover, the respective air pressures must be balanced when uniformly pressing the entire wafer.
In view of the foregoing, it is an object of the present invention to provide a wafer polishing apparatus which is capable of easily changing an area for pressing the wafer.
In order to achieve the above-described object, the present invention provides a wafer polishing apparatus in which a wafer is pressed against a polishing pad so as to polish the wafer, comprising: a carrier; air spout openings provided to the bottom of said carrier, said air spout openings spouting air so as to form the air layer between said carrier and said wafer in order to press the wafer against the polishing pad by the air layer to polish the wafer; air bags provided to the bottom part of wafer carrier for forming said air layer and for partially pressing the top face of said wafer; and pressing area regulating members which are detachable from the bottom of said carrier for regulating an area where said air bag presses the top face of said wafer, wherein said pressing area regulating members regulate different areas to be pressed, and said pressing area regulating members can be replaced so that an area for pressing said wafer with said air bag is changed.
According to the present invention, pressing areas of the wafer can be easily changed by a simple operation, replacing the pressing area regulating members.